1. Field of the Disclosure
The present disclosure relates to an antenna-equipped touch panel. The touch panel is a display unit and an input unit of a device having a radio communication function and that is equipped with a communication antenna.
2. Description of the Related Art
A touch panel is used as a display unit and an input unit of a device, such as a smartphone, a cellphone, or a tablet terminal. Such devices are equipped with a radio-communication transmission/reception antenna. Such devices have installed therein a touch panel having a touch detection function, and an antenna having a radio-signal transmission/reception function and provided separately from the touch panel.
A detection electrode of the touch panel and an antenna element may both be formed from a conductive film. Therefore, if an antenna-equipped touch panel is manufactured and is installed in such devices, for example, manufacturing steps of such devices are simplified, and space for components is saved.
A touch panel includes electrodes and wires (called second wires) that are electrically connected to the electrodes (see, for example, Japanese Unexamined Patent Application Publication No. 2010-238052). In the present disclosure and in the present specification, a planar region in the touch panel where the electrodes are disposed is called an electrode area, and a planar region in the touch panel where the second wires are disposed is called a second wire area.
In equipping the touch panel with an antenna, when the antenna is disposed in the second wire area, the second wires and the antenna are superimposed upon each other in plan perspective view. When the antenna is disposed in the electrode area, the electrodes and the antenna are superimposed upon each other in plan perspective view.
The antenna is normally in a low impedance state. The impedance of the electrodes of the touch panel is normally higher than that of the antenna.
When the antenna is superimposed upon the electrodes and the second wires, which are structural elements of the touch panel, electrical coupling occurs between the antenna and the electrodes and between the antenna and the second wires even if they are not in contact with each other. The electrical coupling adversely affects the detection characteristics of the touch panel. Examples of the adverse effects are: (1) false detection in which, although the touch panel is not being touched, a touch-operation signal is issued, or, in which although the touch panel is being touched, a touch-operation signal is not issued; and (2) a ghost phenomenon in which a touch operation is detected at a location that differs from a location that is touched.